ticdc/log: suppress duplicated log to avoid flooding

[zhaoxinyu]

What problem does this PR solve?

#3524 and #4006

What is changed and how it works?

Add log sampling config items into cdc server config. We use zap.SamplingConfig to efficiently determine whether to drop or write a log.
For example, we set the configs as follows:

server_configs:
  cdc:
    log.sampling.initial: 100
    log.sampling.thereafter: 100

And if the server wants to write 200 same messages into log, only 101 messages (indexed by [0~99, 199]) could be written to log, the remaining 99 messages are supposed to be dropped.

Check List

Tests

• Unit test
• Integration test

Release note

None

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[liuzix]

Can this sampling be scoped? I.e., can it only filter logs from some packages, but not others? Using sampling on some mission critical modules might cause difficulty debugging.

[zhaoxinyu]

Can this sampling be scoped? I.e., can it only filter logs from some packages, but not others? Using sampling on some mission critical modules might cause difficulty debugging.

@liuzix No, at present, zap only supports global sampling configuration, it cannot filter logs based on package name.

[ben1009]

Can this sampling be scoped? I.e., can it only filter logs from some packages, but not others? Using sampling on some mission critical modules might cause difficulty debugging.

+1， btw

[2021-11-26T12:27:32.822Z] --- FAIL: TestServerConfigMarshal (0.01s)

[2021-11-26T12:27:32.822Z]     server_config_test.go:32: 

[2021-11-26T12:27:32.822Z]         	Error Trace:	server_config_test.go:32

[2021-11-26T12:27:32.822Z]         	Error:      	Not equal: ```

[codecov-commenter]

Codecov Report

Merging #3641 (8796269) into master (24030f8) will increase coverage by 1.5517%.
Report is 2809 commits behind head on master.
The diff coverage is 53.3333%.

Additional details and impacted files

@@               Coverage Diff                @@
##             master      #3641        +/-   ##
================================================
+ Coverage   56.5356%   58.0874%   +1.5517%     
================================================
  Files           211        241        +30     
  Lines         22798      24501      +1703     
================================================
+ Hits          12889      14232      +1343     
- Misses         8598       8845       +247     
- Partials       1311       1424       +113     

[ti-chi-bot]

@zhaoxinyu: PR needs rebase.

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[hi-rustin]

@zhaoxinyu Do you have time to advance it?

[zhaoxinyu]

@zhaoxinyu Do you have time to advance it?

This PR is preempted by other high-priority things. I will keep advancing it after completing things in this sprint.

[zhaoxinyu]

/hold